In a connector used for connection of electric wires of automobiles etc., a fitting type connection terminal composed of a combination of a male terminal and a female terminal is used. In recent years, electrical components have been mounted in the engine room of automobiles, and there is a need for the connector to ensure electrical characteristics (low contact resistance) after the lapse of a long time at high temperature.
When a copper alloy sheet strip with a surface coating layer, in which a Sn layer is formed as the surface coating layer on the outermost surface, is held over a long time under a high temperature environment, contact resistance increases. Meanwhile, for example, Patent Document 1 (JP 2004-68026 A as Patent Document 1 is incorporated by reference herein) discloses that a surface coating layer to be formed on a surface of a base material (copper alloy sheet strip) is provided with a three-layer structure of ground layer (made of Ni, etc.)/Cu—Sn alloy layer/Sn layer. According to the surface coating layer having this three-layer structure, a ground layer suppresses diffusion of Cu from the base material and a Cu—Sn alloy layer suppresses diffusion of the ground layer, whereby, low contact resistance can be maintained even after the lapse of a long time at high temperature.
Patent Documents 2 and 3 (JP 2006-77307 A as Patent Document 2 and JP 2006-183068 A as Patent Document 3 are incorporated by reference herein) disclose that a surface coating layer of a copper alloy sheet strip with a surface coating layer, in which a surface of a base material is subjected to a roughening treatment, is provided with the above-mentioned three-layer structure.
Patent Document 4 (JP 2010-168598 A as Patent Document 4 is incorporated by reference herein) discloses that, in a surface coating layer having a three-layer structure of Ni layer/Cu—Sn alloy layer/Sn layer, a Cu—Sn alloy layer is composed of two phases of a ε (Cu3Sn) phase at the Ni layer side and a η (Cu6Sn5) phase at the Sn phase side, and an area coating ratio of the ε phase, with which the Ni layer is coated, is adjusted to 60% or more. To obtain this surface coating layer, there is a need that a reflow treatment is composed of a heating step, a primary cooling step and a secondary cooling step; and a temperature rise rate and a reaching temperature are precisely controlled in the heating step, a cooling rate and a cooling time are precisely controlled in the primary cooling step, and a cooling rate is precisely controlled in the secondary cooling step. Patent Document 4 discloses that this surface coating layer enables maintenance of low contact resistance even after the lapse of a long time at high temperature, and also enables prevention of peeling of the surface coating layer.
A Cu—Ni—Sn—P-based copper alloy sheet strip disclosed, for example, in Patent Documents 5 and 6 (JP 2006-342389 A as Patent Document 5 and JP 2010-236038 as Patent Document 6 are incorporated by reference herein) is used as a base material which forms a surface coating layer whose outermost surface is a Sn layer. This copper alloy sheet strip has excellent bending workability, shear punchability and stress relaxation resistance, and a terminal formed from this copper alloy sheet strip is excellent in stress relaxation resistance, so that the terminal has high holding stress even after the lapse of a long time at high temperature, thus enabling maintenance of high electric reliability (low contact resistance).